Tomic and Stosur both began their singles matches well on Saturday night at the Perth Arena against Canadian pair Milos Raonic and Eugenie Bouchard, but neither could keep it going after the first set as the Australians lost the tie before the mixed doubles were even played.
The result will make it difficult for Australia to now make the final of the round-robin competition to begin the summer of tennis in the mixed team tournament as the home nation attempts to win the Hopman Cup for just the second time.
The Australian pairing, coming into the Hopman Cup as the No. 7 seeds, will now need to win their upcoming clashes with Italy and Poland to be any chance of still making next Saturday's final.
It's not surprising that the Australian team is the best drawcard at the tournament in Perth so the organisers will be desperately hoping for a better showing for Tomic and Stosur for the rest of the week to keep interest and crowds alive.
Having Australia lose, particularly in such disappointing fashion with the way Tomic and Stosur played, was the worst possible result for Hopman Cup organisers after a day of bad news capped off by a horror week leading into the tournament.
Just over a week ago, rising Polish star Jerzy Janowicz withdraw with a foot injury leaving the No. 1 seeded Poland team heavily relying on world No. 5 Agnieszka Radwanska.
Then just a day out from the opening of the Hopman Cup, Spanish veteran and world No. 18 Tommy Robredo pulled out with a foot injury with the former two-time winner unable to partner Anabel Medina Garrigues.
The Hopman Cup got underway on Saturday with Poland's Radwanska and Grzegorz Panfil taking on the Italian team of Flavia Pennetta and Andreas Seppi, but it was scarcely a contest with Seppi retiring due to illness in his singles clash handing Poland the three rubbers to nil victory.
That result all but rubs Italy out of the running for the final with Seppi in danger of not being able to take any further part in the action as well.
With that as the background, the Hopman Cup badly needed a good performance from the Australian team to provide the tournament with some positive vibes.
First up on Saturday night was the men's singles match with Tomic and Raonic, and the early signs were encouraging for the Australian.
Tomic was able to stay with the big-serving Canadian throughout the first set forcing a tie-break, but after a tight battle the world No. 11 Raonic prevailed eight points to six.
Rather than continue to fight hard, though, Tomic simply threw in the towel for the second set and didn’t even deserve to win the one game that he ended up with.
The 21-year-old petulant Australian world No. 51 did not want to continue to compete despite the urging of the Perth crowd and Raonic cruised to the comfortable 7-6 (8), 6-1 victory to give Canada the one-nil lead in the tie.
That put some pressure on Stosur to get the win to force a deciding mixed doubles and the former Grand Slam winner looked good in the first set taking it out 6-4.
However, her serve deserted her in the second set and she continued to shank far too many ground strokes and the 19-year-old rising Canadian star took full advantage.
Bouchard rose to No. 32 in the world by the end of the 2013 season having been ranked well into the hundreds 12 months ago, and she showed more consistency and a cooler head than her more experienced opponent.
The Canadian ended up cruising to the 4-6, 6-2, 6-3 victory to secure the victory for her nation and to put them right on track to be in contention for the Hopman Cup final.
The same can't be said for Australia, though, and even though Stosur never gave up, her game did let her down and Tomic was left with no excuses for his lack of effort in the second set against his Canadian opponent Raonic who desperately wants to become a Grand Slam contender in 2014.
The Australians then had to still come out for the mixed doubles with a win crucial to keeping any hopes of still reaching the final alive, and Stosur and Tomic managed to beat the Canadians 6-2, 6-4.